Just my 2¢ from experience fasting for similar periods, you will lose muscle, but not a significant amount in that time. If you’re approaching a show, I’d think twice about it, but if not, you won’t lost any significant mass. You will look and feel flat af due to having absolutely no carbs during that time, but you will quickly bounce back once you return to feeding/training.
Are you planning on training at all during fast?
In my experience, I’ve done extended fasts, and when I lifted at light to moderate intensity during the fast I didn’t notice any muscle loss. I’m female, 32 years old, 125lbs, \~17% bf, and I’m not trying to compete or increase my lift numbers, so I’m more loosey goosey on it than others.